Features

European Report

By Sean Milmo, Ink World European Editor | October 21, 2005

The need for higher standards of safety and hygiene in food products, combined with changes in eating patterns, is boosting demand for flexible packaging in Europe.

At the same time, printing on flexible packaging is presenting its own technological challenges, providing opportunities for producers of specialty inks, printing chemicals and even makers of the main substrates of plastics and aluminum foil.

As a result, a broad range of companies are now vying to gain footholds in the burgeoning sector for flexible packaging supplies. It is becoming a printing market with the potential for many high-margin niche segments.

There could be scope for close cooperation between ink, chemical and plastic and metal producers. This could lead to partnerships between the three groups or in certain specialty areas mergers between ink and chemical businesses.

Consolidation along the packaging supply chain is creating many points of entry into the sector as it become increasingly complex and sophisticated.

“Among ink producers, especially, there has been so much consolidation in the packaging market in Europe that it is delivering a lot of opportunities to the smaller players,” said Mattheas Wolfgruber, chief executive of Altana Chemie AG, Germany, a leading producer of overprint varnishes for the European flexible packaging market.

“Flexible packaging segments are growing at annual rates ranging from 5 percent to 15 percent,” he said. “The big volume producers of inks and chemicals cannot meet the constantly changing needs of all those different segments. Flexible packaging is becoming a specialty business with a strong service element where customers are willing to pay for higher performance and quality.”

Altana, which already provides adhesives, sealants and a variety of coatings for the flexible packaging market, is seeking acquisitions to make itself a major force in the sector.

“It is quite possible that we may acquire an ink producer, as long as it is a specialty operation,” Mr. Wolfgruber said. “Our customers would appreciate a supplier which is able to offer both chemicals and inks.

“Packaging materials will rely more and more on chemical expertise as a growing number of chemicals have to be applied to the printing process,” he added. “This will mean working across a range of technologies and combining them together.”

Shrink Inks
Among the variety of inks used in flexible packaging, shrink inks are having to meet the some of the biggest technological requirements. They have to stick firmly to various substrates, have a high level of color fastness and be temperature resistant as well as have shrinking properties. They also need a certain coefficient of friction (COF) so that the surface tension is neither too low nor too high.

There is a growing demand for shrink inks in Europe as major brands see shrink sleeves on cans and bottles as a means of gaining a more powerful decorative effect.

“Sleeve applications are definitely increasing,” said Niklas Olsson, product manager for narrow web inks at ANI Printing Inks, Trelleborg, Sweden. “There are a lot of people looking at their potential although not all are actually converting to the system.”

“In low to medium shrink requirements of up to 60 percent, we recommend that all the types of shrink inks be used, but with high shrink requirements of more than 65 percent, solvent, waterborne and UV cationic are the best options,” said Mr. Olsson. “But because of the issue of emissions of volatile organic compounds (VOC), there is a preference among some packaging printers for water-based or UV cationic in this segment.”

With all shrink inks and the vast majority of other flexible packaging inks, however, the surfaces of the substrates have to be pretreated. “The surface tension of the substrate has to be higher than the surface tension of the ink to achieve proper adhesion,” noted Mr. Olsson.

Inks, varnishes and adhesives tend not to adhere well to plastics because of their poor wettability.

“These problems are reflected in poor print performance on plastic substrates, poor resolution and ineffective adhesion after printing,” said Mike Mordente, head of marketing for inks and imaging at Ciba Specialty Chemicals. “This results in considerable wastage for the printer. Additionally, current surface treatments tend to be non-homogeneous and show aging with time.”

A variety of physical and chemical treatments such as flame, corona and plasma can be applied to polymer surface to enhance wettability and adhesion. But these have deficiencies due to low thermal or chemical resistance and formation of weak surface bonds.

“Furthermore, the chemical treatment requires additional process steps,” Mr. Mordente said. “Solvent-based primers are commonly used today but these do not limit emissions of VOCs, in particular when subsequent coatings and inks are solvent-free. In addition they are not as effective for adhesion improvement when radiation-curable coatings are used.”

Ciba has attempted to solve these adhesion difficulties by raising the surface tension on plastic substrates. The plastic surface is first activated through a conventional treatment like corona or plasma. A reactive photoinitiator is then grafted onto the polymer surface to raise its adhesion capabilities.

“The technology has been shown to promote outstanding adhesion properties with no impairment of gloss or brilliance, indeed in some cases actually improving these features,” said Mr. Mordente. “It is the first technology that provides homogeneous, durable plastic surface modification.

“The photoinitiator reacts during polymerization, forming a chemical bond between the ink and polymer surface,” he said.

Ciba claims that the application of the company’s Prime IT technology raises the levels of surface tension on polyethylene, polypropylene and polyethylene terephthalate (PET) substrates by between 30 percent and 47 percent.

Technological Advances
A lot of R&D work is now directed at using more radical means than conventional chemical treatments to change the surfaces of polymers in packaging for more efficient printing and other purposes.

Researchers at Sheffield University in northeast England have developed ways of altering the properties of surfaces by attaching specific molecular groups to the polymer with different pH levels.

“These sort of (molecular) systems might allow you to control the surface properties of a packaging material depending on the external environment,” said Professor Richard Jones, a polymer science expert at the university who is involved in research projects on packaging.

“For example, you could have a surface with pores in it, which are the result of the alignment of the polymer molecules,” he said. “You could change the alignment by changing the ionization of the system by shifting the pH. In this way you could open or close the pores in a controlled way, changing the permeability of the layer.”

The importance of surface characteristics in packaging polymers has already prompted plastic producers in Europe to provide resins which ensure a higher degree of printability.

The attention being given to the interface between inks and polymer surfaces offers opportunities to broad-based companies whose activities embrace polymers, coatings and dispersions as well as inks and their ingredients.

BASF, which in addition to making inks and printing plates produces polymers and specialty chemicals including pigments, has a joint research project between its polymer and printing system operations on improving printing on packaging materials. This is centered on the development of dendritic or hyperbranched polymers which can be incorporated in the inks.

The objective is to eliminate the necessity for different ink systems to be used with polar film materials like polyester and polyamide and non-polar ones such as polyethylene or polypropylene.

The introduction of hyperbranched polymers into the inks allows a single printing system to be applied with both polar and non-polar plastics, according to Bernd Bruchmann, a BASF polymer researcher. The dendritic polymers attach themselves to the pigments in the ink while also anchoring themselves to the plastic surface.

Still, for large numbers of ink makers, particularly smaller ones, the immediate task is the creation of multi-purpose or substrate-specific inks which rely on existing technologies.

Linx Printing Technologies, St. Ives, England, a specialist in ink jet printers and inks for coding and traceability data on packaging, believes that its portfolio of approximately 30 inks is suitable for not only most flexible but also rigid substrates. Its products are generally used at the end of the manufacturing process when goods are ready for distribution.

“We have gone back to first principles, because our customers have extremely high speed production lines and have no opportunity for surface and other treatments,” said Paul Doody, head of Linx’s ink development team.

“We have a multi-disciplinary development group of polymer and material scientists, adhesion and adhesive experts and ink jet ink specialists,” he said. “We don’t have the same quality demands as for normal packaging inks. But our inks do have to achieve a high level of durability with a minimal use of solvents.”

The success of the inks of a specialist company like Linx demonstrates that in the buoyant European flexible packaging market, there will be room for a wide variety of ink technologies, many of which will operate independently of integrated printing systems.

About the author
European Editor Sean Milmo is an Essex, U.K.-based writer specializing in coverage of the chemical industry.